The specific activities of aldolase of cytosols isolated from the livers of 30-31 month old female mice were significantly lower (40%) than those isolated from 2.5 or 7.5 month old female animals. This age decrement results from structural changes in the adolase molecule as indicated by a 30% decrement in the specific activity of the purified enzyme. Induction of aldolase in young and old animals by feeding a high fructose-no fat diet for two days resulted in a two-fold increase in the specific activity of the cytosol. The specific activity of the enzyme purified from these cytosols did not differ as a function of age and was equal to that observed in normal young animals. These data suggested that the age-associated decrease in the specific activity of purified aldolase from old animals must result from post-translational modifications. The ingestion of certain apparently nutritionally acceptable salt mixtures and low protein levels results in a shortening of life span. Intermittently fed animals ate approximately 30% less than control animals with 40% of their intake being ingested within the first three hours of feeding and 60% during the remainder of the 24 hour period.